Bleeding Brake lines on a 1939 Ford Deluxe

[Kube]

Originally Posted by jayvee34

Please explain why single reservoir master cylinders do not require bleeding,
while double reservoir master cylinders do. In reality are not double
reservoirs separated into front and rear brakes, which would be the same as
two single reservoirs? Not being negative about this, I just want to learn
if I am wrong about my thinking. Thanks.

John, A dual cylinder is just that, one having two reservoirs. There is a check valve in this type of system that should one axle (brakes) fail, the valve will shut the respective reservoir off, thus, allowing the driver a bit more time to come to a safe stop.
A single cylinder would quickly lose all pressure and as such would not allow a safety factor of time to stop.
A dual master cylinder will often "trap' air directly between the two reservoirs (in the plunger area). Single units do not have a similar area.

[jayvee34]

Originally Posted by Kube

A dual master cylinder will often "trap' air directly between the two reservoirs (in the plunger area). Single units do not have a similar area.

Thanks very much for the explanation, really appreciated.
I knew the difference and why a double is much safer.

[Mart]

It might be a little brevity in the wording. With reference to BENCH bleeding. While peoples experiences may vary, it is commonly accepted that single reservoir cylinders do not need BENCH bleeding while most people say duals are better off for being BENCH bled first.
All systems on a vehicle need bleeding. That's a given.

[FlatheadTed]

We fitted a new M/C to a chevy caprice bench bleed the MC fitted it then bleed it at the ist pipe connection s got a good pedal ,it was good to go no bleeding at the wheels needed, M/C is up on the fire wall .Also we re kitted a M/C on a English Morris Oxford that has the M/c low in the floor like a 39 Ford ,could not get a pedal (Air Lock ) with the M/C 3/4 full we shoved a wade of rag in the top of the cylinder in the hole then with a air gun set at 40psi pressurized the M/C forced the air out ,(you must not run out of Fluid ) doing this , worked real good ,Ted

[Ramblin Reck]

Originally Posted by Ramblin Reck

We have gone thru 2 Quarts of DOT 3 brake fluid trying to get the brakes bled but no luck.

We had a leak in one of the cylinders but we fixed that.

All brake lines are new, new master cylinder and new wheel cylinders.

We have fluid in the lines out to the bleeder valves.

Only about a thimble of fluid goes into the master cylinder and quickly overflows out of the fill hole.


We believe that if we had a threaded funnel so that constant brake fluid would be keeping the master filled would help. Does such a tool exist?



All helpful comments will be appreciated. Thanks

And I have received many but I have to make confession now. The Brand New MC supplied had a 1 inch square plug cap with a 1/2" Hollow Hex plug in it. The old one did not. We ASSUMED INCORRECTLY that the 1/2" Hex Plug was where one would put the DOT3 Fluid and the larger hole was for doing warranty work. Also it had a mark on it to show if it had been tampered with, we assumed again incorrectly. WRONG! That 1/2" hole actually serves as a breather hole to get air into the MC and release air when needed thru a hollow breather cap. What a Rookie mistake! No wonder it was taking so little fluid each time I poured it into the funnel with the rest going to waste. I have now bought a 1" Open end wrench with a box end on other end and we will see if using it vertically with a long screw driver inserted thru the box end if we can open the big nut. If not then we will remove the MC from the car and put it in a vise which is what we should have done initially. Hindsight, yeah right. My good friend who is actually doing all of the tube bending and heavy grunt work has done a superb job. I should have caught this error. Lesson learned. Even the supplier said that a note should be included with the kit about this fact and the fact that extra torque is usually applied at the factory when installing the 1" fill plug. It does have bench mark on the plug to show where it was torqued to on the MC body. I think we are very close to getting the brakes bled properly and correctly. It has been a learning experience, sho nuff! At least we weren't flying airplanes that day! Onward and upward! Hope this helps someone who travels this road! I know I have learned a lot from this experience!



Later on in this thread I mentioned that I did cobble together a funnel that would screw into the smaller 1/2" hole but it would have been painfully slow i am advised

[Ramblin Reck]

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One word of caution! We got the 1" Square nut off of the MC after it was installed on the car. This is NOT recommended as it it torqued down really tight. It took a herculean effort of a very strong friend to use a vertical 1" open end wrench to remove that nut. put it in a vise BEFORE you install it.



The brake job is complete and we are rolling and stopping. Thanks to everyone who offered advice.

[Mart]

Re the 1" square nut. I went on ebay and bought the cheapest 1" drive socket I could find. I then pushed a long nut into the hex side of the socket and use that as an adaptor to undo the cap.
Mart.

[Ramblin Reck]

Originally Posted by Mart

Re the 1" square nut. I went on ebay and bought the cheapest 1" drive socket I could find. I then pushed a long nut into the hex side of the socket and use that as an adaptor to undo the cap.
Mart.

Huh? Somebody had to draw me a picture, so I now understand. What I cannot find is a 1" Drive Socket on eBay or anywhere else. To remove a tire off of a JCB earth mover, they must use 1" socket or maybe larger! Not that I need it now since my much younger helper was able to remove the 1" Cap nut off of the Master cylinder using the suggested 1" Open End Wrench in the vertical position. But I do appreciate the suggestion from Mart. Thanks. I am also thinking that a 1" Crow Foot socket might have worked also

[jayvee34]

Originally Posted by Mart

Re the 1" square nut. I went on ebay and bought the cheapest 1" drive socket I could find. I then pushed a long nut into the hex side of the socket and use that as an adaptor to undo the cap.
Mart.

That is called ingenuity!!! Great idea.

[Bertha]

Old bucklenuster here...I still use my 16oz clear pop bottle when I flush & bleed single-handed with a vacuum bleeder. Fill the bottle with denatured alcohol, (after draining) fill the MC & bottle, turn the bottle upside down in the MC so you can watch the level, do the same with the new fluid. I wrap the MC with shop towels to keep things clean, better a few drips that air in the lines.👍

[nvtinman]

Don't know if this would work for you but among my various parts I had a master cylinder cap that looked more like steel or maybe cast aluminum rather than the cast iron caps most of them had. I drilled and tapped it so I could put a fitting to use my pressure bleeder.
I don't know how or where I picked it up but wonder if a person could do the same thing with a cast plug? It doesn't seem like my bleeder put everything under much pressure.
Anyway it allowed me to bleeder the system by myself.

[19Fordy]

That 1 in. square nut on the 40 master cylinder should not be THAT tight. It does have a gasket on it. You should be able to loosen it with a crescent wrench. Firm is fine.
Also, I found Speed Bleeders to be big help.

[mrtexas]

IMHO new shoes aren't any good unless fitted to the drums. You won't be able to bleed and get a good pedal until shoes are fitted, assuming you have original Ford shoes and backing plates. That is a good reason to get bendix brake backing plates and shoes to avoid the hassle of fitting the shoes to the drums. I trashed canned a number of Ford lockheed backing plates since they couldn't be even given away!

The bleeding problems are due to either non fitted shoes and with master cylinder lower than the brake cylinders. The vacuum bleeders work quite well. I use them.

I've solved my brake bleeding problems on stock 41 and rod 49 by using modern bendix backing plates(which don't require fitting just adjusting) and remote brake fluid reservoirs mounted on the firewall above the MC. I also use a modern corvette dual master cylinder.